Trees Are Losing Leaves, But Fungi Are Growing

Nature Notes

November 22, 2009|By Dan Summers

As daylight continues to grow shorter and autumn's temperatures decrease, the reproductive cycles of most living things are put on hold until winter's grip is finally broken by the welcome increase of warmth and light. For fungus, however, this is a prime season for putting energy into reproducing. Wherever there is damp ground, decaying leaves, rotten wood - in our yards, roadsides, parks and woodlands - we don't have to search long to find a fascinating variety of fungus - just look for mushrooms.

Mushrooms may look like some sort of odd plant, but what we see above the ground is the fruiting body or spore-producing part of an underground network of fungus. Although there are a multitude of different kinds of fungus in our region, most prefer the spring and fall seasons to produce the familiar above-ground structures that produce and release spores. When we look under the caps of many common types of mushrooms, we can see the gills - flaps of tissue that look like the spread out pages in a book held upside down; it's on the surface of these gills that the spores are produced. These microscopic cells are spread by wind or water to where they can enter the soil and start a new fungus structure.

Ready for some fungi vocabulary? If the spores end up in a location with just the right temperature, moisture and food source, they will start to grow hyphae - tiny nutrient-gathering threads that spread out in all directions. The entire network of underground hyphae is called the mycelium, which is often described as looking something like a subterranean cobweb.

A fungal mycelium is not a network of roots; unlike a plant's roots, a mycelium doesn't anchor a plant, connect to a stem with leaves or store the food products of photosynthesis. What a mycelium does is spread throughout new sources of fungal food such as old wood, leaf litter and rotten fruit and release special chemicals (enzymes) that break down complex organic materials into simple products (sugars). These are then absorbed into the cells of the fungus, which provide the energy for the fungus to continue to grow. The left-overs at the end of a fungal feast are the products of decomposition - a wealth of nutrients and organic materials that become part of the soil and are ready for recycling into the web of life.

The variety of outdoor trail and garden habitats at the Virginia Living Museum are great places to spot mushrooms - they give away the hiding places of fascinating fungi!

Dan Summers is the school education curator at the Virginia Living Museum. Visit the museum online at www.thevlm.org.